Solution spray apparatus and solution spray method

ABSTRACT

A solution spray apparatus includes a nozzle which sprays a droplet of a solution such as EL solution, a heater is provided on the nozzle to heat the solution in the nozzle to a temperature lower than a boiling point of the solution in the nozzle, so that the droplet of the heated solution is ejected from the spray to an object.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2003-018543, filed Jan. 28,2003; and No. 2003-018578, filed Jan. 28, 2003, the entire contents ofboth of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solution spray apparatus and solutionspray method which spray a droplet or droplets onto a substrate.

2. Description of the Related Art

An organic EL (ElectroLuminescent) element is constituted by stacking ananode electrode, an organic EL layer which is formed from an organicmaterial and emits light by internal flow of a current, and a cathodeelectrode. When a forward bias voltage exceeding a threshold is appliedbetween the anode and cathode electrodes, the organic EL layer emitslight. Such organic EL elements are arrayed as pixels in a matrix on asubstrate to realize an organic EL display panel which displays an imageby causing each organic EL element to emit light at a predeterminedtonal luminance.

In an active matrix organic EL display panel formed by a plurality ofpixels, one of the anode and cathode electrodes can be designed as acommon electrode connected to all pixels. However, at least the otherelectrode and the organic EL layer must be patterned for each pixel. Amethod of patterning an electrode for each pixel can adopt aconventional semiconductor device manufacturing technique. Morespecifically, an electrode can be patterned for each pixel by properlyperforming the film formation step of an electrode material film by PVD,CVD, or the like, the mask step by photolithography or the like, and theshaping step of the electrode material film by etching or the like.

Organic EL layer formation methods can be roughly classified into dryvapor deposition and wet coating in accordance with conditions such asthe material. In dry vapor deposition, a hard mask having an opening ina region where an organic EL layer is to be formed is interposed betweena substrate and a vapor deposition source formed from an organic ELlayer material. The organic EL layer material which is heated andvaporized is applied into a film in the target region on the substrate.In wet coating, an organic EL layer can be patterned for each pixel byapplying an ink-jet technique, as disclosed in Jpn. Pat. Appln. KOKAIPublication No. 2000-106278. That is, droplets of an EL solutionprepared by dissolving as a solute a polymer organic EL material for anorganic EL layer in a solvent are sprayed from a nozzle, and an organicEL layer is patterned for each pixel. In wet coating to which theink-jet technique is applied, the film formation step and the patterningstep for each pixel can be almost simultaneously performed. An organicEL layer need not be etched and patterned using a photoresist mask.

In order to provide an organic EL display panel which displays ahigh-resolution image, the organic EL layer must be micropatterned. Theink-jet method can micropattern an organic EL layer because the dropletdiameter of the EL solution is very small. However, droplets run andspread till solidification after landing, and droplets of organic ELlayers in adjacent pixels may mix. To prevent this, a matrix-likepartition which isolates each pixel from the surrounding pixels is used.A droplet which lands in a region surrounded by the partition is stoppedby the partition, preventing mixture of droplets in adjacent pixels.Particularly when the emission color is different between adjacentpixels, organic EL layer materials which are different in accordancewith the emission color hardly mix. The color purity of the emissioncolor is expected to improve.

The polymer organic EL material generally has a low solubility in thesolvent. The use of a solvent the solubility of which is low, requires alarge amount of solvent in order to fully dissolve the solute. The timetaken to evaporate the solvent after droplets of the EL solution land islong, resulting in low productivity. In order to form an organic ELlayer into a film thickness suitable for emission, spraying of dropletsof a low-concentration EL solution from an ink-jet nozzle andevaporation of droplets after landing on a substrate must be repeated aplurality of number of times, also resulting in low productivity. If thedroplet amount sprayed at once is increased to decrease the count of thedroplet spray step, a droplet readily overflows over the partition.Droplets in adjacent pixels mix to degrade the image quality. If thepartition is formed high so as to prevent overflow of droplets, filmformation of the partition takes a long time, and an electrode formed onthe organic EL layer may be cut off by the partition step.

As a solvent which easily dissolves the polymer organic EL material, anorganic solvent such as xylene is sometimes employed. However, suchorganic solvent exhibits high volatility; it vaporizes in an ink-jetnozzle, and the polymer organic EL material segregates to clog theink-jet nozzle.

It is therefore an object of the present invention to efficientlydeposit a solution at only a target position with high precision.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, as shown in, e.g.,FIG. 2,

a solution spray apparatus comprises

a nozzle or nozzles (e.g., nozzle 55) which sprays one or more dropletsof a solution, and

a heater (e.g., nozzle heat-insulating unit 59) which heats the solutionin the nozzle to a temperature lower than a boiling point of thesolution in the nozzle.

According to the present invention, the solution in the nozzle is heatedby the heater, so that a liquid component contained in a droplet sprayedfrom one or more spray ports of the nozzle easily evaporates. Inparticular, during flying of a droplet till landing onto a desiredregion or regions after spraying from the spray port or ports, theliquid component such as the solvent of the droplet graduallyevaporates. The droplet lands with a small droplet volume and highsolute concentration. The time until the solvent completely evaporatesafter the droplet lands is short.

Since a droplet becomes small by heat during flying, no landed dropletruns off from a desired position. When different droplets are appliedonto desired adjacent regions, no solutions in the adjacent regions mix.A larger-volume droplet of even a solvent the solubility of which islow, can be sprayed at once. The spray count necessary to form thesolute to a proper film thickness in a desired region can be decreased.

Since the solution is heated, the solubility in the solvent can beincreased to prevent segregation of the solute in the nozzle includingthe spray port. This prevents nozzle clogging, and makes the filmthickness by droplets uniform because of a uniform dropletconcentration.

The heater heats the solution in the nozzle to a temperature lower thanthe boiling point of the solution in the nozzle. Generation of bubblesby volatilization of the solution in the nozzle can be suppressed. As aresult, leakage of the solution from the spray port upon a change insolution pressure in the nozzle caused by bubbles can be suppressed. Ina solution spray apparatus such as a piezoelectric solution sprayapparatus which sprays a solution by a pressure increase in the nozzlecaused by mechanical displacement of a piezoelectric element, bubbles inthe nozzle change in volume in accordance with mechanical displacementof the piezoelectric element, inhibiting a pressure increase. Theinternal pressure of the nozzle does not increase, and clogging occursin solution spraying. To prevent this, the heater heats the solution soas to suppress generation of bubbles, and a desired amount of solutioncan be sprayed.

The solution spray apparatus may adopt relative movement means (e.g.,head 54, work table 51, or driving device 52) for moving one of thenozzle and substrate relatively to the other.

The solution spray apparatus can further manage the temperature byfurther comprising

measurement means for measuring a temperature of the solution in thenozzle, and

temperature control means (e.g., temperature controller 61) forcontrolling the heater so as to keep the temperature of the solution inthe nozzle constant on the basis of the temperature measured by themeasurement means. The temperature can be managed at high precision, anda droplet can be properly sprayed.

According to another aspect of the present invention, as shown in, e.g.,FIG. 3,

another solution spray apparatus comprises

a nozzle or nozzles (e.g., nozzle 55) which sprays one or more dropletsof a solution,

a tank (e.g., organic material solution tank 56) which stores thesolution and supplies the solution to the nozzle, and

a heat-insulating unit (e.g., heat-insulating unit 58) whichheat-insulates the solution in the tank.

According to the present invention, the solution in the tank isheat-insulated by the heat-insulating unit, the heat-insulated solutionis supplied to the nozzle, and a droplet or droplets are sprayed from aspray port or ports of the nozzle. Since the solution is heat-insulated,the solvent contained in the droplet easily evaporates. In particular,during flying of a droplet till landing onto a desired region afterbeing sprayed from the spray port, the solvent of the droplet graduallyevaporates. The droplet lands on a desired region with a small dropletvolume and high solute concentration. The time until the solventcompletely evaporates after the droplet lands may be short.

Since a droplet becomes small by heat during flying, no landed dropletruns off from a desired region, and no solutions in desired adjacentregions mix. Thus, a larger-volume droplet of even a solvent thesolubility of which is low, can be sprayed at once. The spray countnecessary to form the solute to a proper film thickness in a desiredregion can be decreased.

Since the solution is heat-insulated, the solubility in the solvent canbe increased to prevent deposition of the solute in the spray port ornozzle. This prevents nozzle clogging, and makes the film thickness bydroplets uniform because of a uniform droplet concentration.

The heat-insulating unit preferably heat-insulates the solution in thetank so as to be lower than the boiling point of the solution in thetank.

The solution spray apparatus can further manage the temperature at highprecision by further comprising measurement means for measuring atemperature of the solution in the tank, and temperature control meansfor controlling the heat-insulating unit so as to keep the temperatureof the solution in the tank constant on the basis of the temperaturemeasured by the measurement means.

According to still another aspect of the present invention, as shown in,e.g., FIG. 5,

a solution spray apparatus comprises

a table (e.g., work table 51) which supports a substrate,

at least one nozzle (e.g., nozzle 55) which ejects one or more dropletsof a solution onto one surface of the substrate, and

a heat-insulating unit (substrate heat-insulating unit 63) whichheat-insulates the table.

According to the present invention, the substrate is heat-insulated, andthe temperature of an atmosphere from the nozzle or nozzle spray port toa desired region is increased and kept increased. The liquid containedin a droplet easily evaporates till landing onto a desired region by theeffect of heat-insulating the solution in the nozzle in advance and theeffect of heat-insulating a sprayed droplet during flying.

Since the solvent of the droplet that lands on the substrate quicklyevaporates, no landed droplet runs off from a desired region, and nosolutions in desired adjacent regions mix. A larger-volume droplet ofeven a solvent the solubility of which is low, can be sprayed at once.The spray count necessary to form the solute to a proper film thicknessin a desired region can be decreased.

The solution spray apparatus may adopt relative movement means formoving one of the table and nozzle relatively to the other.

According to still another aspect of the present invention, as shown in,e.g., FIG. 7,

a solution spray apparatus comprises

a table (e.g., work table 51) which supports a substrate,

at lest one nozzle (e.g., nozzle 55) which sprays at least one dropletof a solution onto one surface of the substrate, and

a radiator (e.g., radial heat-insulating unit 64) which radiates heattoward a space between the nozzle and the substrate.

According to the present invention, heat is radiated to the spacebetween the nozzle and the substrate, and the temperature of anatmosphere from the nozzle or nozzle spray port to a desired region isincreased and kept increased. The solvent contained in a droplet easilyevaporates till landing onto a desired region by the effect ofheat-insulating the solution in the nozzle in advance and the effect ofheat-insulating a sprayed droplet during flying. In particular, duringflying of a droplet till landing onto a desired region after sprayingfrom the spray port, the solvent of the droplet gradually evaporates.The droplet lands with a small droplet volume and high soluteconcentration. The time until the solvent completely evaporates afterthe droplet lands is short.

Since a droplet becomes small by heat during flying, no landed dropletruns off from a desired region, and no solutions in desired adjacentregions mix. For this reason, a larger-volume droplet of even a solventof the solubility of which is low, can be sprayed at once. The spraycount necessary to form the solute to a proper film thickness in adesired region can be decreased.

According to still another aspect of the present invention, as shown in,e.g., FIG. 9,

a solution spray apparatus comprises

one or more nozzle (e.g., nozzle 55) which spray a droplet or dropletsof a solution onto one surface of a substrate,

a substrate heat-insulating unit (e.g., substrate heat-insulating unit63) which heat-insulates the substrate, and

cooling means (e.g., cooling medium jacket 69) for cooling the solutionin the nozzle.

According to the present invention, the nozzle is cooled. Even in theuse of a solution containing a low-boiling-point solvent orhigh-vapor-pressure solvent, a proper amount of solution can be sprayedwhile generation of a vaporized component in the solution stayed in thenozzle is suppressed. Since the substrate is heat-insulated, a dropletis quickly heated to dry the solvent in the solution until it reaches adesired region on the substrate. The droplet amount decreases toincrease the solution viscosity. No droplet flows out and scatters froma desired region, and the time till evaporation can be shortened.

According to still another aspect of the present invention, as shown in,e.g., FIG. 9,

a solution spray apparatus comprises

at least one nozzle (e.g., nozzle 55) which sprays one or more dropletof a solution onto one surface of a substrate, and

circulation means (e.g., cooling medium circulator 170) for circulatinga medium controlled to a predetermined temperature around the nozzle inorder to control the solution in the nozzle to a predeterminedtemperature.

According to this aspect, the temperature of the solution in the nozzlecan be quickly, easily controlled to a predetermined temperature bycirculating the medium.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIGS. 1A and 1B are a plan view and sectional view, respectively,showing an organic EL display panel;

FIG. 2 is a schematic side view showing a solution spray apparatusaccording to the first embodiment of the present invention that is usedto form the organic EL layer of the organic EL display panel;

FIG. 3 is a schematic side view showing a solution spray apparatusaccording to the second embodiment of the present invention;

FIG. 4 is a schematic side view showing a solution spray apparatusaccording to the third embodiment of the present invention;

FIG. 5 is a schematic side view showing a solution spray apparatusaccording to the fourth embodiment of the present invention;

FIG. 6 is a schematic side view showing a solution spray apparatusaccording to the fifth embodiment of the present invention;

FIG. 7 is a schematic side view showing a solution spray apparatusaccording to the sixth embodiment of the present invention;

FIG. 8 is a schematic side view showing a solution spray apparatusaccording to the seventh embodiment of the present invention;

FIG. 9 is a schematic side view showing a solution spray apparatusaccording to the eighth embodiment of the present invention;

FIG. 10 is a graph showing the relationship between the elapsed time ofdroplet spray operation and the nozzle temperature;

FIG. 11 is a schematic side view showing a solution spray apparatusaccording to the ninth embodiment of the present invention;

FIG. 12 is a schematic cross sectional view showing a solution sprayapparatus according to the tenth embodiment of the invention; and

FIG. 13 is a schematic cross sectional view showing a modification ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

(First Embodiment)

The first embodiment of the present invention will be described belowwith reference to several views of the accompanying drawing.

FIG. 1A is a plan view showing an organic EL display panel 1. FIG. 1B isa sectional view taken along the line (IB)—(IB) in FIG. 1A.

The organic EL display panel 1 comprises a transparent substrate 2 onwhich a plurality of pixels are formed. An organic EL element is formedin each pixel. An example of the transparent substrate 2 is a glasssubstrate such as a silica glass substrate or borosilicate glasssubstrate.

A plurality of transparent electrodes 3 are arrayed and formed in amatrix on one or upper surface of the transparent substrate 2. Thetransparent electrode 3 has a relatively high work function, and servesas the anode electrode of the organic EL element. The transparentelectrode 3 is formed form a conductive, light-transmitting material.The transparent electrode 3 is formed from at least one materialselected from the group consisting of, e.g., indium-tin-oxide (ITO),indium-zinc-oxide, indium oxide (In₂O₃), tin oxide (SnO₂), and zincoxide (ZnO).

On the upper surface of the transparent substrate 2, is mounted apartition 6 which has a matrix shape obtained by coupling a plurality ofwalls along the row direction and a plurality of walls along the columndirection at intersections. When viewed from the top, the partition 6surrounds each transparent electrode 3 with its walls and partitions apixel in each surrounded region. The partition 6 is formed from at leastone insulating material selected from the group consisting of aphotosensitive resin (e.g., polyimide resin), silicon oxide, and siliconnitride.

An organic EL layer 4 is formed on the transparent electrode 3 in eachregion surrounded by the walls of the partition 6. The organic EL layer4 is the light-emitting layer of the organic EL element in a broadsense, and includes layers exhibiting electron injection, electrontransportation, hole injection, and hole transportation. The organic ELlayer 4 contains a light-emitting material (fluorescence) capable of wetfilm formation, such as a polymer organic compound (thiophene-basedpolymer, polyfluorene-based polymer, or the like). The organic EL layer4 may have a three-layered structure of, sequentially from thetransparent electrode 3, a hole transportation layer which transportsholes upon application of a predetermined voltage, a light-emittinglayer in a narrow sense which emits light upon injection of electronsand holes, and an electron transportation layer which transportselectrons upon application of a predetermined voltage. Alternatively,the light-emitting layer may have a two-layered structure of,sequentially from the transparent electrode 3, a hole transportationlayer and a light-emitting layer in a narrow sense. The light-emittinglayer may have a one-layered structure of a light-emitting layer in anarrow sense. The light-emitting layer may have a multilayered structurein which an electron- or hole-injected layer is interposed betweenproper layers in each of the above layered structures. Thelight-emitting layer may have still another layered structure. Theorganic EL layer 4 has a function of transporting holes and electrons toa recombination region, and a function of generating excitons byrecombination of holes and electrons in the recombination region to emitlight. The organic EL layer 4 has any one of an organic EL layer 4Rwhich is separated for each pixel and emits red light, an organic ELlayer 4G which emits green light, and an organic EL layer 4B which emitsblue light. As shown in FIG. 1A, a plurality of pixel lines on which theorganic EL layers 4R are arranged, a plurality of pixel lines on whichthe organic EL layers 4G are arranged, and a plurality of pixel lines onwhich the organic EL layers 4B are arranged are repetitively arrayedsequentially from the left. These organic EL layers 4 are formed by adroplet spray or eject method using a solution spray or eject apparatus50 (to be described later).

Although not shown in FIG. 1A, a counter electrode 7 is formed on theorganic EL layers 4, as shown in FIG. 1B. The counter electrode 7functions as a cathode electrode including a low-work-function layerwhich is arranged on a surface in contact with the organic EL layers 4and formed from a material with a relatively low work functioncontaining, e.g., indium, magnesium, calcium, lithium, barium, or ametal or alloy containing at least one of them, and a high-work-functionlayer which is arranged on the low-work-function layer and formed fromaluminum, chromium, or the like. The counter electrode 7 may be formedas one electrode connected to all pixels, or as a plurality ofelectrodes electrically insulated for each pixel.

In each pixel, when a voltage is so applied as to set the potential ofthe transparent electrode 3 higher than that of the counter electrode 7,holes are injected from the transparent electrode 3 to the organic ELlayer 4. At the same time, electrons are injected from the counterelectrode 7 to the organic EL layer 4, and the organic EL layer 4 emitslight.

If the organic EL display panel 1 is driven by an active matrix method,each pixel is provided with a pixel circuit which is connected to anyone of a plurality of scanning lines (not shown) along the row directionin order to select a predetermined pixel during a selection period, andconnected to any one of a plurality of data lines (not shown) along thecolumn direction in order to supply a predetermined current to theorganic EL layer 4 of the selected pixel. The pixel circuit includespluralities of thin-film transistors and capacitors. During an emissionperiod after the selection period, a predetermined current is suppliedvia the transparent electrode 3 to the organic EL layer 4 of a pixelselected in the selection period.

The solution spray apparatus 50 which forms the organic EL layer 4 bythe droplet spray method will be explained.

FIG. 2 is a schematic side view showing the solution spray apparatus 50.

The solution spray apparatus 50 forms the organic EL layer 4 by sprayingor ejecting droplets of an EL solution 71 onto the transparent substrate2. One droplet sprayed to each region surrounded by the partition 6 isabout 2 to 100 pl. The solute of the EL solution 71 is an organicmaterial for the organic EL layer 4 (material capable of wet filmformation containing at least any one of a light-emitting substance,hole transportation substance, and electron transportation substance).The solvent of the EL solution 71 is a material capable of dissolvingthe organic material of the organic EL layer 4. An example of thissolvent is tetramethylbenzene with a boiling point higher than roomtemperature. A material having higher volatility enhances the effects ofthe present invention. In forming the organic EL layer 4, thetransparent substrate 2 on which a plurality of transparent electrodes 3and the partition 6 are formed in advance is used. In FIG. 2, thepartition 6 and transparent electrodes 3 on the transparent substrate 2are not illustrated.

The solution spray apparatus 50 comprises a work table 51, a drivingdevice 52, a guide 53, a head 54, a nozzle 55, an organic materialsolution tank 56, an EL solution supply pipe 57, a first heat-insulatingunit 58, a second heat-insulating unit 59, and a controller 60. The worktable 51 has a flat, horizontal upper surface and is movable in thesub-scanning direction (direction perpendicular to the sheet surface).The driving device 52 moves the work table 51 in the sub-scanningdirection. The guide 53 extends in the main scanning direction(direction parallel to the sheet surface) substantially perpendicular tothe sub-scanning direction. The head 54 is a moving member which isguided by the guide 53 and moves in the main scanning direction alongthe guide 53. The nozzle 55 has one or more ports to spray a droplet ordroplets of the EL solution 71 toward the substrate 2. The organicmaterial solution tank 56 serves as the supply source of the EL solution71. The EL solution supply pipe 57 supplies the EL solution 71 from theorganic material solution tank 56 to the nozzle 55. The firstheat-insulating unit 58 is arranged around the organic material solutiontank 56, and has a heating resistor which heats the EL solution 71 inthe organic material solution tank 56 to 30° C. or more by an electricalsignal. The second heat-insulating unit 59 is arranged around the nozzle55, and has a heating resistor which heats the EL solution 71 in thenozzle 55 to 30° C. or more by an electrical signal. The controller 60controls the whole solution spray apparatus 50.

The work table 51 is flat, and the transparent substrate 2 having thetransparent electrodes 3 and partition 6 provided thereon is set on theupper surface of the work table 51.

The organic material solution tank 56 stores the EL solution 71, and hasthe first heat-insulating unit 58. The first heat-insulating unit 58desirably heats the EL solution 71 stored in the organic materialsolution tank 56 to a temperature higher than room temperature so as notto boil the EL solution 71 stored in the organic material solution tank56. Since the EL solution 71 is sealed in the organic material solutiontank 56, the organic material solution tank 56 prevents a change in theconcentration of the EL solution 71 in the organic material solutiontank 56 caused by volatilization of the solvent in the EL solution 71.The organic material solution tank 56 also prevents mixture of externaldust into the EL solution 71 in the tank 56.

The driving device 52 conveys the work table 51 together with thetransparent substrate 2 in the sub-scanning direction in synchronismwith the operation of the head 54. More specifically, the driving device52 intermittently conveys the transparent substrate 2. The drivingdevice 52 is controlled by the controller 60.

The head 54 reciprocates in the main scanning direction along the guide53 above the work table 51 in synchronism with intermittent conveyanceof the transparent substrate 2. More specifically, while the transparentsubstrate 2 stops, the head 54 reciprocates at least once in the mainscanning direction. The driving of head 54 is controlled by thecontroller 60.

The nozzle 55 is arranged at the lower portion of the head 54. Thenozzle 55 communicate with the organic material solution tank 56 via theEL solution supply pipe 57. The EL solution 71 is supplied from theorganic material solution tank 56 to the nozzle 55 via the EL solutionsupply pipe 57, and filled in the nozzle 55. One or a plurality of sprayports 55 a are arranged at the lower end of the nozzle 55, and thenozzle 55 has a spray means. The nozzle 55 sprays droplets of the ELsolution 71 from the spray port or ports 55 a toward the transparentsubstrate 2 by the operation of the spray means. The distance from thespray port 55 a to the transparent substrate 2 is desirably short forthe precision of the droplet landing position on the transparentsubstrate 2. However, the distance is preferably long to a certaindegree in order to suppress splash of droplets landed on the transparentsubstrate 2 to the nozzle 55. Considering these two conditions, thedistance is preferably about 1.0 mm to 1.5 mm. The time until thedroplet of the EL solution 71 are sprayed from the spray port 55 a andreach the transparent substrate 2 is preferably 1 to 100 msec.

The spray means arranged in the nozzle 55 may be a piezoelectric means,electrostatic means, thermal jet means, or the like. The piezoelectricspray means changes the volume of a piezoelectric element to increasethe internal pressure of the nozzle 55, and thus sprays a droplet of theEL solution 71 from the spray port 55 a. The electrostatic spray meansapplies a voltage to a capacitor in contact with the EL solution 71 inthe nozzle 55, changes the attraction or repulsion of the capacitorelectrode, increases the pressure of the solution in the nozzle 55, andsprays a droplet of the EL solution 71 from the spray port 55 a. Thethermal jet spray means instantaneously film-boils, by a heating member,the EL solution 71 in the nozzle 55 in contact with the heating member,generates bubbles in the EL solution 71, increases the internal pressureof the nozzle 55, and sprays a droplet of the EL solution 71 from thespray port 55 a.

Either the transparent substrate 2 or nozzles 55 is relatively movedalong a plane parallel to the upper surface of the work table 51 by thework table 51, driving device 52, and head 54.

The nozzle 55 has the second or nozzle heat-insulating unit (heatkeeping unit) 59. The second heat-insulating unit 59 compensates for aheat amount deprived when the EL solution 71 passes through the ELsolution supply pipe 57 and the like. The second thermal insulator 59heats the EL solution 71 in the nozzle 55 to a temperature of 30° C. ormore so as not to boil the EL solution 71 in the nozzle 55. The secondheat-insulating unit 59 is different from a thermal jet heating member.More specifically, the thermal jet heating member instantaneously heatsthe EL solution 71 to film-boil the EL solution 71 only when the ELsolution 71 is sprayed. To the contrary, the second heat-insulating unit59 heats the entire EL solution 71 in the nozzle 55 so as not to boilthe EL solution 71. Further, the driving temperature keeps a steadystate.

An organic material for the organic EL layer 4, in the EL solution 71changes depending on the emission color, and organic EL layers 4 of aplurality of organic materials are formed from corresponding nozzles 55for corresponding pixels at once. In this case, EL solutions 71containing these organic materials are stored in different organicmaterial solution tanks 56, and a plurality of nozzles 55 coupled to therespective organic material solution tanks 56 are arranged. For example,an EL solution 71 for the organic EL layer 4R which emits red light isstored in a red organic material solution tank 56 while being heated bya first red heat-insulating or heat-keeping unit 58 so as not to boil.The EL solution 71 reaches a red nozzle 55 heated by a second redheat-insulating unit 59 via a red EL solution supply pipe 57. An ELsolution 71 for the organic EL layer 4G which emits green light isstored in a green organic material solution tank 56 while being heatedby a first green heat-insulating unit 58 so as not to boil. The ELsolution 71 reaches a green nozzle 55 heated by a second greenheat-insulating unit 59 via a green EL solution supply pipe 57. An ELsolution 71 for the organic EL layer 4B which emits blue light is storedin a blue organic material solution tank 56 while being heated by afirst blue heat-insulating unit 58 so as not to boil. The EL solution 71reaches a blue nozzle 55 heated by a second blue heat-insulating unit 59via a blue EL solution supply pipe 57.

At this time, the first, red, green, and blue heat-insulating units 58may be set to different heating temperatures as far as the units 58 areheated enough to dissolve corresponding organic materials in solventswithout boiling in accordance with the properties of the organicmaterials. The second, red, green, and blue heat-insulating units 59 maybe set to different heating temperatures as far as they are heatedenough to dissolve corresponding organic materials in solvents withoutboiling in accordance with the properties of the organic materials.

The above-described work table 51 and nozzle (nozzles) 55 areincorporated in a housing 70. Sub-scanning movement of the transparentsubstrate 2, spraying of droplets of the EL solution 71 from the nozzle55, and landing of droplets of the EL solution 71 on the transparentsubstrate 2 are performed in the internal space of the housing 70.

The controller 60 controls the driving device 52, head 54, and nozzle(or nozzles) 55 to operate or stop them at predetermined timings.

A method of manufacturing the organic EL display panel 1 will beexplained.

A plurality of transparent electrodes 3 are patterned into a matrix on atransparent substrate 2 by properly performing a film formation step byPVD, CVD, or the like, a mask step by photolithography or the like, anda thin-film shaping step by etching or the like.

A resist film of a photosensitive resin such as polyimide is formed onone surface of the transparent substrate 2 having the transparentelectrodes 3 by spin coating, dipping, or the like. The resist film isexposed and partially removed with a developing solution, therebyshaping the resist film so as to surround each transparent electrode 3.The remaining resist film serves as the partition 6. The partition 6 ofsilicon oxide or silicon nitride may be formed by properly performing afilm formation step by PVD, CVD, or the like, a mask step byphotolithography or the like, and a thin-film shaping step by etching orthe like.

The transparent substrate 2 having the transparent electrodes 3 andpartition 6 is set on the work table 51. The solution spray apparatus 50is used to eject a droplet of the EL solution 71 to each regionsurrounded by the walls of the partition 6, thereby forming an organicEL layer 4 in each region surrounded by the partition 6.

More specifically, each unit of the solution spray apparatus 50 iscontrolled by the controller 60 and operates as follows.

The driving device 52 intermittently conveys the transparent substrate 2together with the work table 51 in the sub-scanning direction. While thetransparent substrate 2 stops, the head 54 reciprocates at least once inthe main scanning direction.

While the head 54 moves in the main scanning direction, the nozzle 55passes immediately above the transparent electrode 3 of each pixelsurrounded by the partition 6. While the nozzle 55 passes above thetransparent electrode 3, the nozzle 55 sprays one or a plurality ofdroplets of the EL solution 71 toward the transparent electrode 3 ofeach pixel. Note that the head 54 may be so moved as to position thenozzle port to a predetermined position of the transparent electrode 3and then temporarily stopped. The nozzle 55 may spray one or a pluralityof droplets of the EL solution 71 through its port, toward thetransparent electrode 3. This operation may be repeated to sequentiallyform the organic EL layers 4 on the transparent electrodes 3.

A droplet that lands on the transparent electrode 3 spreads into a filmand solidifies to form an organic EL layer 4.

After the head 54 reciprocates at least once in the main scanningdirection, as described above, the driving device 52 conveys thetransparent substrate 2 together with the work table 51 by apredetermined distance in the sub-scanning direction. After thetransparent substrate 2 stops again, reciprocation of the head 54 andspraying of the EL solution 71 from the nozzle 55 are executed again.The solution spray apparatus 50 repeats the above-mentioned operation toform organic EL layers 4 in all regions surrounded by the walls of thepartition 6.

While the solution spray apparatus 50 operates, the firstheat-insulating unit 58 heats the EL solution 71 in the organic materialsolution tank 56 so as not to boil the EL solution 71, and the secondheat-insulating unit 59 heats the EL solution 71 in the nozzle 55 so asnot to boil the EL solution 71. During flying of a droplet of the ELsolution 71 till landing onto the transparent electrode 3 after sprayingfrom the spray port 55 a, the solvent in the droplet evaporates togradually decrease the droplet volume. When the droplet lands, thevolume becomes small to suppress splash of the landed droplet. Thus, nodroplet runs off from a region surrounded by the partition 6.

Since the EL solution 71 is heated in the nozzle 55, the solubility inthe solvent increases to increase the concentration of the organicmaterial. This can thicken the organic EL layer 4 formed by one dropletspray from the port. The droplet spray count for forming the organic ELlayer 4 having a predetermined thickness can be decreased to shorten themanufacturing time of the overall organic EL display panel 1.

Since a heated droplet of the heated EL solution 71 is sprayed, thesolvent in the droplet quickly evaporates by heat during flying beforethe droplet lands. The time taken for evaporation after landing can alsobe shortened to shorten the manufacturing time of the overall organic ELdisplay panel 1.

Since the EL solution 71 is heated, the solubility in the solvent isincreased. The organic material hardly deposits in the spray port orports 55 a, preventing clogging of the spray port 55 a.

Since the first and second heat-insulating units 58 and 59 heat the ELsolution 71 so as not to boil it, the pressure of the EL solution 71 inthe nozzle 55 or organic material solution tank 56 does not abruptlychange. A droplet from the spray port 55 a of the nozzle 55 does notland at a position different from a desired one, such as a positionimmediately above the partition 6.

In this manner, the organic EL layer 4 is formed in each surroundedregion. When the organic EL layer 4 has a multilayered structure of,e.g., a hole transportation layer, a light-emitting layer in a narrowsense, and an electron transportation layer, the solution sprayapparatus 50 is prepared for each layer. These layers are sequentiallyformed by the above-described way, thereby forming the organic EL layers4.

After the end of forming the organic EL layers 4 by the solution sprayapparatus 50, a film formation step by PVD, CVD, or the like isperformed to form a counter electrode 7 on one surface of thetransparent substrate 2 on which the organic EL layers 4 are formed.

Since the first embodiment sprays a heated droplet, no droplet runs off,and no EL solutions 71 in two adjacent pixels mix on the partition 6.The droplet volume which can be sprayed at once can be increased todecrease the spray count necessary to form the organic EL layer 4 havinga predetermined thickness.

(Second Embodiment)

A solution spray apparatus 150 as shown in FIG. 3 may be used as anapparatus which forms an organic EL layer 4. The same reference numeralsas those of the building components of the solution spray apparatus 50denote the same building components of the solution spray apparatus 150,and a detailed description thereof will be omitted.

The solution spray apparatus 150 comprises a temperature controller 61in addition to the arrangement of the solution spray apparatus 50 shownin FIG. 2. The temperature controller 61 controls heating by first andsecond heat-insulating units 58 and 59. More specifically, an organicmaterial solution tank 56 incorporates a temperature measurement unit(thermometer) 78 which measures the temperature of an EL solution 71.The measured temperature is fed back from the temperature measurementunit 78 to the temperature controller 61. The temperature controller 61controls the first heat-insulating unit 58 so as to keep the EL solution71 in the organic material solution tank 56 constant on the basis of themeasured temperature. Similarly, nozzle 55 incorporates a temperaturemeasurement unit 78 which measures the temperature of the EL solution71. The measured temperature is fed back from the temperaturemeasurement unit 78 to the temperature controller 61. The temperaturecontroller 61 controls the second heat-insulating unit 59 so as to keepthe temperature of the EL solution 71 in the nozzle 55 constant on thebasis of the measured temperature. By controlling the first and secondheat-insulating units 58 and 59 by the temperature controller 61, the ELsolution 71 is kept heated at a predetermined temperature so as not toboil.

In the solution spray apparatus 150, the temperature of the EL solution71 in the nozzle 55 and organic material solution tank 56 is controlledconstant, and the EL solution 71 does not boil. The pressure of the ELsolution 71 is stable, and sprayed droplets always have the samesolubility and temperature. Sprayed droplets always have the sameconcentration and amount and take the same evaporation time, and thusthe film thicknesses of formed organic EL layers 4 become uniform.

(Third Embodiment)

A solution spray apparatus 250 as shown in FIG. 4 may be used as anapparatus which forms an organic EL layer 4. The same reference numeralsas those of the building components of the solution spray apparatus 50denote the same building components of the solution spray apparatus 250,and a detailed description thereof will be omitted.

The solution spray apparatus 150 comprises a heat insulator 62 inaddition to the arrangement of the solution spray apparatus 50 shown inFIG. 2. The heat insulator 62 is interposed between a head 54 and nozzleor nozzles 55 so as to be sandwiched between them. The heat insulator 62prevents conduction of the heat of the nozzle 55 heated by first andsecond heat-insulating units 58 and 59 to the head 54. If the head 54 isheated, it expands and cannot be positioned at high precision, and thedroplet landing position may deviate. However, in the solution sprayapparatus 250, the heat insulator 62 suppresses heating of the head 54,and no sprayed droplet causes any landing error on a partition 6.

In the solution spray apparatus 250, the head 54 may be arranged movablynot only in the main scanning direction but also in the sub-scanningdirection. At this time, a work table 51 may or may not move in thesub-scanning direction.

(Fourth Embodiment)

A solution spray apparatus 350 as shown in FIG. 5 may be used as anapparatus which forms an organic EL layer 4. The same reference numeralsas those of the building components of the solution spray apparatus 50denote the same building components of the solution spray apparatus 350,and a detailed description thereof will be omitted.

Instead of the first and second heat-insulating units 58 and 59 of thesolution spray apparatus 50 shown in FIG. 2, the solution sprayapparatus 350 comprises a substrate heat-insulating unit 63 having aheating resistor which heats upon supply of an electrical signal. Theremaining building components are the same as those of the solutionspray apparatus 50. The substrate heat-insulating unit 63 is buried in awork table 51, and heats a transparent substrate 2 from the work table51. By heating the transparent substrate 2 by the substrateheat-insulating unit 63, heat is transferred to nozzle 55 to heat thesolution therein. The solvent in droplets heated in the nozzle 55 easilyvaporizes immediately after spraying. The atmosphere above thetransparent substrate 2 is also heated by the substrate heat-insulatingunit 63. A droplet sprayed from a spray port 55 a is heated till landingonto the transparent substrate 2, and the solvent more easily vaporizes.The droplet diameter can be decreased without decreasing the organicmaterial amount in the droplet, and a droplet can be prevented fromsplashing from a landed pixel to an adjacent pixel over a partition 6.The transparent substrate 2 is also heated by the substrateheat-insulating unit 63, and the solvent can be evaporated immediatelyafter a droplet of an EL solution 71 lands, shortening the drying timeand increasing the productivity.

(Fifth Embodiment)

A solution spray apparatus 450 as shown in FIG. 6 may be used as anapparatus which forms an organic EL layer 4. The same reference numeralsas those of the building components of the solution spray apparatus 50denote the same building components of the solution spray apparatus 450,and a detailed description thereof will be omitted.

The solution spray apparatus 450 comprises a heat insulator 67 inaddition to the arrangement of the solution spray apparatus 350 shown inFIG. 5. The heat insulator 67 is interposed between a work table 51 anda driving device 52. The heat insulator 67 prevents conduction of theheat of the work table 51 heated by a substrate heat-insulating unit 63to the driving device 52. If the driving device 52 overheats, itthermally expands. If a controller 60 moves the work table 51 in thesub-scanning direction and a head 54 in the main scanning direction onthe basis of moving amounts programmed in advance, misalignment occursto shift the droplet landing position. In the solution spray apparatus450, however, the heat insulator 67 suppresses heating of the drivingdevice 52, no heat is transferred below the heat insulator 67, and thedriving device 52 does not thermally expand. A transparent substrate 2is formed from glass, has low heat absorption, and hardly thermallyexpands, preventing any droplet landing error. In this structure, thework table 51 may be arranged movably not only in the sub-scanningdirection but also in the main scanning direction. At this time, thehead 54 may or may not move in the main scanning direction.

(Sixth Embodiment)

A solution spray apparatus 550 as shown in FIG. 7 may be used as anapparatus which forms an organic EL layer 4.

Instead of the first and second heat-insulating units 58 and 59 of thesolution spray apparatus 50 shown in FIG. 2, the solution sprayapparatus 550 comprises a radial heater 64 which heats upon supply of anelectrical signal. The radial heater 64 is arranged above a work table51 inside a housing 70 at a position where the radial heater 64 does notinterfere with movement of a head 54 and nozzle 55. The radial heater 64radially dissipates heat toward the space between the nozzle 55 and atransparent substrate 2 to heat droplets sprayed from a spray port 55 a.Also in the solution spray apparatus 550, a droplet is heated duringflying, and the solvent in the droplet evaporates. No landed dropletruns off from a region surrounded by a partition 6, and no EL solutions71 in two adjacent pixels mix on the partition 6. In order to maintainhigh-precision position landing of a droplet, a heater such as aninfrared heater (e.g., the radial heater 64) which transfers heatwithout any wind is preferable.

(Seventh Embodiment)

A solution spray apparatus 650 as shown in FIG. 8 may be used as anapparatus which forms an organic EL layer 4.

Instead of the radial heater 64 of the solution spray apparatus 550shown in FIG. 7, the solution spray apparatus 650 comprises a fan 66 anda heating unit 65 having a heating resistor which heats upon supply ofan electrical signal. The heating unit 65 and fan 66 are arranged abovea work table 51 inside a housing 70 at a position where they do notinterfere with movement of a head 54 and nozzle 55. The heating unit 65generates heat, and the fan 66 fans hot air from the heating unit 65 tothe space between the work table 51 and the nozzle 55. The heat of theheating unit 65 is radiated by the fan 66 to the space between thenozzles 55 and a transparent substrate 2 to heat a droplet sprayed froma spray port 55 a. Also in the solution spray apparatus 650, a dropletis heated during flying, and the solvent in the droplet evaporates. Nolanded droplet runs off from a region surrounded by a partition 6, andno EL solutions 71 of two adjacent pixels mix on the partition 6.

(Eighth Embodiment)

A solution spray apparatus 750 according to the eighth embodiment of thepresent invention will be described. FIG. 9 is a schematic side viewshowing the solution spray apparatus 750 according to the eighthembodiment.

The solution spray apparatus 750 comprises a work table 51, a drivingdevice 52, a guide 53, a head 54, at least one nozzle 55, an organicmaterial solution tank 56, an EL solution supply pipe 57, a substrateheat-insulating unit 63, a cooling medium jacket 69, a cooling mediumcirculator 170, a cooling medium supply pipe 81, a cooling mediumdischarge pipe 82, and a controller 60. The work table 51 has a flat,horizontal upper surface and is movable in the sub-scanning direction.The driving device 52 drives the work table 51 so as to move the worktable 51 in the sub-scanning direction. The guide 53 extends in the mainscanning direction substantially perpendicular to the sub-scanningdirection. The head 54 is a moving member which is guided by the guide53 and moves in the main scanning direction along the guide 53. Thenozzle 55 sprays an organic EL solution 71 as a droplet. The organicmaterial solution tank 56 serves as the supply source of the organic ELsolution 71. The EL solution supply pipe 57 supplies the organic ELsolution 71 from the organic material solution tank 56. The substrateheat-insulating unit 63 heats a transparent substrate 2 on the worktable 51. The cooling medium jacket 69 is arranged in direct or indirectcontact with the nozzle 55, receives a cooled cooling medium 77, andcools the nozzle 55 by the temperature of the cooling medium 77. Thecooling medium circulator 170 cools and circulates the cooling medium77. The cooling medium supply pipe 81 supplies the cooling medium 77supplied from the cooling medium circulator 170 to the cooling mediumjacket 69. The cooling medium discharge pipe 82 supplies the coolingmedium 77 discharged from the cooling medium jacket 69 to the coolingmedium circulator 170. The controller 60 controls the whole solutionspray apparatus 750. The cooling medium 77 may be a liquid such as asolution or pure water containing a coolant (e.g., alcohol, diethyleneglycol, or potassium chloride) as far as the cooling medium 77 can beutilized as a fluid which can move through the cooling medium supplypipe 81 and cooling medium discharge pipe 82 and can be easily cooled.Also, the cooling medium 77 may be a cooled gas, or include a liquidcrystal phase containing cooled crystallized solid particles.

The transparent substrate 2 and nozzle 55 are relatively moved along aplane parallel to the upper surface of the work table 51 by the worktable 51, driving device 52, and head 54. FIG. 9 shows only one nozzle55 and one organic material solution tank 56. In practice, a pluralityof organic material solution tanks 56 are arranged, and a plurality ofnozzles 55 are arranged in the head 54. More specifically, organic ELsolutions 71 in each of which an organic material for emitting light inany one of red, green, and blue is dissolved are filled in correspondingorganic material solution tanks 56. The nozzle 55 which communicateswith each organic material solution tank 56 sprays the organic ELsolution 71 in which the organic EL material for emitting light in anyone of red, green, and blue is dissolved.

The cooling medium circulator 170 comprises a tank which stores thecooling medium 77, a cooler which cools the cooling medium 77 in thetank, a pump which pumps the cooling medium 77 of the tank, and adischarge means which discharges the cooling medium 77 to the tank. Thecooling medium circulator 170 supplies the cooling medium 77 cooled inthe tank to the cooling medium jacket 69 via the cooling medium supplypipe 81 by the pump. The cooling medium jacket 69 transfers cool air ofthe supplied cooling medium 77 to the nozzles 55 to deprive the nozzles55 of heat and cool the nozzles 55. The cooling medium jacket 69 may bearranged on part of the surfaces of the nozzles 55, as shown in FIG. 9.Alternatively, the cooling medium jacket 69 may be so arranged as tosurround the nozzles 55 in order to increase the cooling efficiency.

The cooling medium 77 which absorbs the heat of the nozzles 55 in thecooling medium jacket 69 is discharged to the cooling medium circulator170 via the cooling medium discharge pipe 82. The cooling mediumcirculator 170 incorporates the cooler to cool the cooling medium. Thecooling medium 77 can also be cooled by arranging in at least one of thecooling medium supply pipe 81 and cooling medium discharge pipe 82 acooler which electrically cools the cooling medium. When the coolingmedium circulator 170 does not incorporate any means for cooling acooling medium supplied from the cooling medium discharge pipe 82, thecooling medium 77 which is supplied from the cooling medium jacket 69and heated by the heat of the nozzles 55 may be discharged outside thesolution spray apparatus 750. In this case, fresh cooled cooling medium77 is externally received in accordance with the discharge amount of thecooling medium 77, and sent to the cooling medium supply pipe 81. Inthis structure, the nozzles 55 can be cooled without any cooling time ofthe heated cooling medium 77.

The controller 60 sets the temperature in the solution spray apparatus750 to be lower than that of the organic EL solution 71 in the nozzles55. As a result, the temperatures of the cooling medium supply pipe 81and cooling medium discharge pipe 82 can be decreased to cool thecooling medium 77 in the pipes which moves in contact with the coolingmedium supply pipe 81 and cooling medium discharge pipe 82.

A pattern is formed by spraying a droplet of the organic EL solution 71in which the organic EL material is dissolved, from a spray port 55 a toeach of pixels formed by a partition 6 on the transparent substrate 2and a transparent electrode 3, as shown in FIGS. 1A and 1B. In thiscase, if the solvent of the organic EL solution 71 has a low volatilityor high boiling point, the organic EL solution 71 cannot be quicklydried. A solution droplet may exceed the partition 6 by the landingforce on the transparent electrode 3, and flow out to an adjacent pixel.

To prevent this, the solution spray apparatus 750 uses the substrateheat-insulating unit 63 to heat, e.g., the work table 51 and thetransparent substrate 2 set on the work table 51. Since the transparentsubstrate 2 and its upper atmosphere are heated, a droplet is heatedimmediately when it is sprayed from the spray port 55 a of the nozzle55. The solvent in the droplet evaporates or its evaporation is promotedbefore the droplet reaches a pixel. After landing, evaporation of thesolvent in the heated droplet is promoted to quickly dry the droplet.

If, however, the temperature of the work table 51 is increased using anorganic EL solution 71 containing a low-boiling-point solvent orhigh-vapor-pressure (high-volatility) solvent, radial heat is generatedfrom the work table 51, and increases the nozzle 55 and its internaltemperature. As a result, part of the organic EL solution 71 in thenozzle 55 vaporizes. When the nozzle 55 uses a piezoelectric spraymeans, a diaphragm is contracted and expanded by a piezoelectric elementto spray the organic EL solution 71. When the diaphragm expands, theinternal pressure decreases to more readily vaporize the organic ELsolution 71.

If the vaporized solvent amount is small, the vaporized solvent gasdissolves in the solvent solution again without posing any problem.However, when a low-boiling-point solvent or high-vapor-pressure solventis used and the ambient temperature in spraying solvent droplets is high(temperature in the nozzle 55 is high), the vaporized solvent amount islarge, and the vaporized solvent gas hardly dissolves in the solventagain. For example, a PEDOT (PolyEthyleneDiOxyThiophene) solution isused as the organic EL solution 71 in forming the hole transportationlayer of an organic EL layer 4. The PEDOT solution useshigh-vapor-pressure water as a main solvent. If the temperature of thenozzle 55 exceeds 40° C., a gas is confirmed to be generated. The nozzle55 is so set as to be filled with the solution and spray a predeterminedamount (predetermined volume) of solution. If the vaporized solvent gasstays in the nozzle 55 and is mixed in the solution, the organic ELsolution 71 cannot be sprayed by an accurate amount. In some cases, thesolution cannot be sprayed at all. A solvent gas may be sprayed from thespray port 55 a, similar to a liquid solution. However, the amount ofthe organic EL solution 71 per unit volume is much smaller than theamount of liquid solution, and no film can be satisfactorily formed. Asufficient amount of droplet does not reach the transparent electrode 3,and the film thickness of the organic EL layer 4 becomes small. Thetransparent electrode 3 and a counter electrode 7 are electricallyshort-circuited to decrease the yield of an organic EL display panel 1.

To prevent this, the solution spray apparatus 750 cools the organic ELsolution 71 in the nozzles 55 by using the cooling medium jacket 69arranged on the nozzle 55. This suppresses vaporization of the organicEL solution 71 and allows continuously spraying droplets of the organicEL solution 71 by an accurate amount from the nozzles 55.

A method of manufacturing the organic EL display panel 1 will beexplained.

Similar to the first embodiment, a transparent substrate 2 havingtransparent electrodes 3 and a partition 6 is set on the work table 51.At this time, the transparent substrate 2 is heated by the substrateheat-insulating unit 63 via the work table 51. The cooling mediumcirculator 170 supplies the cooling medium 77 to the cooling mediumjacket 69 to cool the nozzle 55. A droplet of the organic EL solution 71is sprayed from at least one spray port 55 a of the nozzle 55 to eachregion surrounded by the walls of the partition 6 by using the solutionspray apparatus 750, forming an organic EL layer 4 in the surroundedregion.

More specifically, each unit of the solution spray apparatus 750 iscontrolled by the controller 60 and operates as follows.

The driving device 52 intermittently conveys the transparent substrate 2together with the work table 51 in the sub-scanning direction. While thetransparent substrate 2 stops, the head 54 reciprocates at least once inthe main scanning direction.

While the head 54 moves in the main scanning direction, the nozzle 55passes immediately above the transparent electrode 3 of each pixelsurrounded by the partition 6. While the nozzle 55 passes above thetransparent electrode 3, it sprays one or a plurality of droplets of theEL solution 71 through its port or ports, toward the transparentelectrode 3 of each pixel.

At this time, the nozzle 55 is cooled by the cooling medium jacket 69.This suppresses the stay of the solvent vaporized by cavitation in theorganic EL solution 71 inside the nozzle 55. A predetermined amount ofdroplet can be continuously sprayed from the spray port 55 a of thenozzle 55. The film thickness of the organic EL layer 4 by landeddroplets does not become nonuniform between adjacent pixels.

By heating the transparent substrate 2, the droplet path is also heated.A droplet sprayed from the spray port 55 a is heated before it reachesthe transparent electrode 3 on the transparent substrate 2. The solventevaporates before the droplet is deposited on the transparent electrode3, and the droplet amount becomes smaller than the spray amount. Theorganic EL solution 71 can therefore be prevented from scattering toadjacent pixel or pixels, or running off over the partition 6. Thisminimizes mixing of organic EL solutions 71 of adjacent pixels indifferent emission colors.

After the head 54 reciprocates at least once in the main scanningdirection, as described above, the driving device 52 conveys the worktable 51 together with the transparent substrate 2 by a predetermineddistance in the sub-scanning direction. After the transparent substrate2 stops again, reciprocation of the head 54 and spraying of the ELsolution 71 from the nozzle 55 are executed again. The solution sprayapparatus 750 repeats the above-mentioned operation to form organic ELlayers 4 in all regions surrounded by the partition 6.

Note that the head 54 may be so moved as to position the nozzle 55 to apredetermined position of the transparent electrode 3 and thentemporarily stopped. The nozzle port 55 a may spray one or a pluralityof droplets of the EL solution 71 toward the transparent electrode 3.This operation may be repeated to sequentially form the organic ELlayers 4 on the transparent electrodes 3.

After the end of forming the organic EL layers 4 by the solution sprayapparatus 750, a film formation step by PVD, CVD, or the like isperformed to form a counter electrode 7 on the organic EL layers 4 onone surface of the transparent substrate 2.

In the solution spray apparatus 750, the organic EL solution 71 sprayedas droplets from the nozzle 55 is heated by the substrateheat-insulating unit 63, and the organic EL solution 71 can be formedinto a film in a desired pixel. The cooling medium jacket 69 suppressesvaporization of the organic EL solution 71 in the nozzle 55 caused byoverheating of the nozzle 55 positioned above the substrateheat-insulating unit 63 by heat transferred from the substrateheat-insulating unit 63, and a desired amount of droplet can be sprayedfrom each nozzle 55. Organic EL layers 4R, 4G, and 4B can maintainthicknesses within a desired range, realizing an expression at a stablebrightness and high emission color purity.

The relationship between the time elapsed after the start of sprayoperation of the organic EL solution 71 and the temperature of thenozzle 55 in the solution spray apparatus will be explained withreference to FIG. 10. FIG. 10 is a graph showing the relationshipbetween the time elapsed after the start of droplet spray operation andthe temperature of the nozzle 55. In this measurement, the PEDOTsolution was used as the organic EL solution 71.

“*”s in the graph of FIG. 10 represent a comparative example in whichthe heater is so controlled as to set the temperature of the work table51 to 70° C. and the nozzle 55 is not cooled by using a solution sprayapparatus obtained by excluding the cooling medium jacket 69, coolingmedium circulator 170, and cooling medium discharge pipe 82 from thesolution spray apparatus 750 in FIG. 9. In this case, when the timeelapsed after the start of spraying droplets of the PEDOT solutionreached 300 sec, the temperature of the nozzle 55 greatly exceeded 40°C. and reached 48.3° C. The solvent of the PEDOT solution vaporized andstayed in the nozzle 55 owing to overheating in the PEDOT solutionsupply line of the nozzle 55. Although the pump performed mechanicaldisplacement, spraying of droplets of the PEDOT solution stopped.Accordingly, continuous spraying stopped.

The solid line in the graph of FIG. 10 represents a case in which thetemperature of the work table 51 is heated to 70° C. in the solutionspray apparatus 750 and the cooling medium circulator 170 is operated tocool the nozzle 55. In this case, even if the time elapsed after thestart of spraying droplets of the PEDOT solution reached 600 sec, thetemperature of the nozzle 55 did not exceed 40° C., and continuous,successive spraying of the PEDOT solution could be realized.

The dotted line in the graph of FIG. 10 represents a case in which thetemperature of the work table 51 is controlled to 80° C. in the solutionspray apparatus 750 and the cooling medium circulator 170 is operated tocool the nozzle 55. In this case, even if the time elapsed after thestart of spraying droplets of the PEDOT solution reached 600 sec, thetemperature of the nozzle 55 did not exceed 40° C., and continuous,successive spraying of the PEDOT solution could be realized.

According to the eighth embodiment, a droplet of the organic EL solution71 is sprayed to a region surrounded by the walls of the partition 6 onthe transparent substrate 2 while the transparent substrate 2 set on thework table 51 is heated by the substrate heat-insulating unit 63 and thenozzle 55 is cooled by the cooling medium jacket 69. Even in the use ofthe organic EL solution 71 containing a low-boiling-point solvent orhigh-vapor-pressure solvent, cooling of the nozzle 55 suppressesgeneration of a vaporized component in the organic EL solution 71 stayedin the nozzle 55. The organic EL solution 71 is filled in the nozzle 55,and a proper amount of the organic EL solution 71 can be sprayed. Sincethe transparent substrate 2 is heated, a droplet is quickly heated todry the solvent in the organic EL solution 71 until the droplet reachesthe heated transparent substrate 2. The droplet amount decreases toincrease the viscosity of the organic EL solution 71. No droplet flowsout to a desired surrounded region or scatter. In addition, the timetill evaporation can be shortened.

(Ninth Embodiment)

The ninth embodiment according to the present invention will bedescribed with reference to FIG. 11. FIG. 11 is a schematic side viewshowing a solution spray apparatus 850 according to the ninthembodiment.

In the eighth embodiment, if the nozzle 55 is excessively cooled withoutany limitation, the temperature of the internal organic EL solution 71excessively decreases to increase the viscosity. The droplet amount ofthe organic EL solution 71 sprayed from the spray port 55 a maydecrease. The ninth embodiment solves this problem by adopting atemperature adjustment means for adjusting a cooling function in acooling medium circulator. The same reference numerals as in thesolution spray apparatus 750 of the eighth embodiment denote the sameparts in the solution spray apparatus 850 of the ninth embodiment, and adescription thereof will be omitted. The solution spray apparatus 850comprises a work table 51, a driving device 52, a guide 53, a head 54,at least one nozzle 55, an organic material solution tank 56, an ELsolution supply pipe 57, a substrate heat-insulating unit 63, a coolingmedium jacket 69 which is arranged on the nozzle 55 and receives acooling medium 77, a cooling medium circulator 170 serving as the supplysource of the cooling medium 77, a cooling medium supply pipe 81, acooling medium discharge pipe 82, a temperature detector 75 whichdetects the temperatures of the nozzles 55, a temperature controller 76which adjusts a cooling function in the cooling medium circulator 170 onthe basis of temperature information of the nozzle 55 that is detectedby the temperature detector 75, and a controller 60 which controls thewhole solution spray apparatus 850.

The cooling medium circulator 170 is a circulation constant-temperaturebath. The cooling medium circulator 170 comprises a tank which storesthe cooling medium 77, a pump which pumps the cooling medium 77, and atemperature change means which heats and cools the cooling medium 77 inthe tank. The pump pumps the cooling medium 77 in the tank to thecooling medium jacket 69 via the cooling medium supply pipe 81. Thecooling medium 77 supplied to the cooling medium jacket 69 deprives thenozzle 55 of heat. The cooling medium 77 that absorbed heat isdischarged to the cooling medium circulator 170 via the cooling mediumdischarge pipe 82. The cooling medium circulator 170 supplies thedischarged cooling medium 77 into the internal tank. The controller 60instructs the cooling medium circulator 170 to set the flow rate of thecooling medium 77 supplied to the cooling medium supply pipe 81 to apredetermined amount in accordance with temperature information from thetemperature detector 75.

The temperature controller 76 controls the temperature change means ofthe cooling medium circulator 170, and adjusts the cooling medium 77 inthe internal tank on the basis of temperature information of the nozzle55 that is detected by the temperature detector 75. Adjustment of thetemperature and/or flow rate is so controlled as to keep the temperatureof the nozzle 55 constant. The controller 60 instructs the temperaturecontroller 76 to set the cooling medium 77 in the cooling mediumcirculator 170 to a predetermined temperature in accordance withtemperature information from the temperature detector 75.

A method of manufacturing an organic EL display panel 1 by using thesolution spray apparatus 850 is almost the same as the method ofmanufacturing the organic EL display panel 1 by using the solution sprayapparatus 750 in the eighth embodiment except the cooling procedure ofthe nozzle 55. To avoid a repetitive description, only the coolingprocedure will be explained.

When a droplet of the organic EL solution 71 is sprayed from at leastone port of the nozzle 55 of the solution spray apparatus 850, thecontroller 60 executes cooling control in accordance with informationfrom the temperature detector 75. More specifically, the cooling mediumcirculator 170 supplies the cooling medium 77 to the cooling mediumjacket 69, and the cooling medium 77 cools the nozzle 55. The substrateheat-insulating unit 63 heats the work table 51 to heat the nozzle 55and its lower atmosphere by radial heat. The temperature controller 76controls the temperature of the cooling medium 77 in the internal tankof the cooling medium circulator 170 so as to properly keep constant thetemperature of the nozzle 55 that is detected by the temperaturedetector 75. In other words, the temperature of the cooling medium 77supplied to the cooling medium jacket 69 is so controlled as to properlykeep the temperature of the nozzle 55 constant by heating and cooling ofthe nozzle 55 and the flow rate balance of the cooling medium 77controlled by the cooling medium circulator 170. The controller 60 alsooutputs a control signal for controlling the flow rate to the coolingmedium circulator 170 on the basis of control information of thetemperature controller 76 that is fed back to the controller 60. Anappropriate temperature of the cooling medium 77 is a temperature atwhich the viscosity of the organic EL solution 71 is set to a propervalue without generating any stay of a vaporized solvent in the organicEL solution 71 inside the nozzle 55. An appropriate temperature of thenozzle 55 may have a predetermined range.

According to the ninth embodiment, the temperature controller 76controls the temperature of the cooling medium 77 supplied to thecooling medium jacket 69 to a temperature at which the viscosity of theorganic EL solution 71 is properly kept constant. Continuous spraying ofdroplets of the organic EL solution 71 can be realized even by using theorganic EL solution 71 containing a low-boiling-point solvent orhigh-vapor-pressure solvent. In addition, a high-quality organic ELdisplay panel in which the viscosity of the organic EL solution 71 isproperly kept constant, the droplet amount sprayed from the nozzle 55 iskept constant, and the film thickness of the organic EL layer isconstant can be manufactured.

(10th Embodiment)

The 10th embodiment according to the present invention will be describedwith reference to FIG. 12. FIG. 12 is a schematic side view showing asolution spray apparatus 950 according to the 10th embodiment.

In the ninth embodiment, the cooling medium circulator 170 cools theorganic EL solution 71 in the nozzle 55. To the contrary, the solutionspray apparatus 950 employs a temperature control medium circulator 171instead of the cooling medium circulator 170. In order to suppress thetemperature rise or drop of an organic EL solution 71 in a nozzle 55caused by an external factor such as a temperature outside the nozzle55, the temperature control medium circulator 171 has a function ofsupplying a temperature control medium 79 set to a predeterminedtemperature via a temperature control medium supply pipe 83 to atemperature control medium jacket 80 arranged in contact with the nozzle55, discharging via a temperature control medium discharge pipe 84 thetemperature control medium 79 whose temperature is changed by the nozzle55 in the temperature control medium jacket 80, returning the dischargedtemperature control medium 79 to the predetermined temperature again bya temperature controller 76, and circulating the temperature controlmedium 79 so as to flow through the temperature control medium supplypipe 83. The temperature controller 76 properly heats or cools thetemperature control medium 79 circulated by the temperature controlmedium circulator 171 to a predetermined temperature. The temperaturecontrol medium 79 is preferably a medium such as diphenyl ether whichhas a large heat capacity per unit volume and high heat transferperformance and is chemically inert to a temperature adjusted by thetemperature controller 76.

In the solution spray apparatus 950, the temperature controller 76 cancool and heat the temperature control medium 79. This can quickly solvethe problem of insufficient volatilization of the solvent when thetemperature of the organic EL solution 71 sprayed from the nozzle 55decreases owing to excessive cooling. Further in the solution sprayapparatus 950, a heat-insulating unit 86 keeps the organic EL solution71 in an organic material solution tank 56 at a predeterminedtemperature regardless of the external temperature. When the heattransfer effect is small due to a small surface area or volume of thenozzle 55, and a large heat capacity is required due to a small amountof the internal organic EL solution 71 or continuous spraying of theorganic EL solution 71, the organic EL solution 71 cannot besatisfactorily controlled to a predetermined temperature by heattransfer from the temperature control medium 79. Even in this case, thesolution can be easily cooled inside the nozzle 55 and evaporatedoutside the nozzle 55 by heat-insulating the organic EL solution 71 to acertain degree.

The present invention is not limited to the above embodiments, andvarious modifications and design changes may be made without departingfrom the gist of the present invention.

For example, the solution spray apparatuses 50, 150, 250, 350, 450, 550,650, 750, and 850 are used to manufacture the organic EL display panel1. These apparatuses can also be used to manufacture a color filter or acolor changing medium which absorbs short-wavelength light and emitslonger-wavelength light. In the color filter or the color changingmedium which changes short-wavelength light into long-wavelength light,a partition is formed in a matrix on a transparent substrate, similar tothe organic EL display panel 1, and colored layers are formed in regionssurrounded by the partition. These colored layers can be formed by thesolution spray apparatus 50, 150, 250, 350, 450, 550, 650, 750, or 850.A material which forms the colored layer is different from one whichforms the organic EL layer 4, but can be dissolved in an organicsolvent.

The head 54 is movable in the main scanning direction in the aboveembodiments, but may be movable in the main scanning direction andsub-scanning direction, i.e., in a plane parallel to the upper surfaceof the work table 51. In this case, the work table 51 may be fixed.Similarly, the work table 51 may be movable in the main scanningdirection and sub-scanning direction by the driving device 52. In thiscase, the head 54 may be fixed. In other words, one of the work table 51and head 54 suffices to be movable relatively to the other in a planeparallel to the upper surface of the work table 51.

The heater which heats the EL solution 71 supplied from the organicmaterial solution tank 56 to the nozzle 55 may be arranged in the ELsolution supply pipe 57. In this case, the heat-insulating unit 58 maynot be arranged around the organic material solution tank 56, and theheat-insulating unit 59 may not be arranged.

At least one of the heat-insulating units 58 and 59 is arranged in thesolution spray apparatus 350, 450, 550, or 650 shown in FIGS. 5, 6, 7,or 8, thereby improving the solvent volatilization effect.

In the eighth to 10th embodiments, the cooling medium jacket 69 (ortemperature control medium jacket 80) is directly or indirectly arrangedin tight contact with the nozzle 55, as an arrangement which holds amedium subjected to temperature control. However, the present inventionis not limited to this. For example, a cooling medium jacket (ortemperature control medium jacket) may be incorporated in the nozzle 55.Alternatively, a cooling medium jacket (or temperature control mediumjacket) may be arranged on, e.g., a stay for attaching the nozzle 55 tothe head 54.

The temperature control means is not limited to these jackets. Thetemperature control means may be a Peltier element which generates atemperature difference in two types of metals by energization andradiates heat, a heat radiation fin, a cooling fan, or the like. Aplurality of members among these members and jackets may be combined.

Only the nozzle 55 is cooled by the cooling medium jacket 69 in theeighth and ninth embodiments, but the present invention is not limitedto this. For example, a heater may be newly attached to the nozzle 55,and one or both of cooling by the cooling medium jacket 69 and heatingby the heater may be executed for the nozzle 55. This arrangement canshorten the time until the temperature of the nozzle 55 reaches a propertemperature by heating the nozzle 55 after the start of activating thesolution spray apparatus 850. The manufacturing time of the organic ELdisplay panel 1 can therefore be shortened as a whole.

The nozzle 55 sprays droplets of the EL solution 71 in a single color inthe above embodiments, but the present invention is not limited to this.As shown in FIG. 13, a red nozzle 55R, green nozzle 55G, and blue nozzle55B which respectively spray EL solutions 71R, 71G, and 71B prepared bydissolving organic materials for EL films for emitting red light, greenlight, and blue light may be simultaneously scanned to simultaneouslyspray droplets of the EL solutions 71R, 71G, and 71B.

The red EL solution 71R stored in an organic material solution tank 56Ris kept at a proper temperature by a red EL solution heat-insulatingunit 86R. While the red EL solution 71R is kept at this temperature, itreaches the red nozzle 55R via a red EL solution supply pipe 57R. Theheat-insulating unit 86R is set at a high temperature in advance inconsideration of a temperature by which the temperature of the red ELsolution 71R decreases by heat transfer to the red EL solution supplypipe 57R or the like. When the red EL solution 71R in the red nozzle 55Roverheats or does not reach a predetermined temperature, the temperaturecontrol medium circulator 171 supplies the temperature control medium 79set to the predetermined temperature into the red nozzle 55R via atemperature control medium supply pipe 83R so as to set the red ELsolution 71R to the predetermined temperature. The temperature controlmedium circulator 171 then receives the temperature control medium 79 inthe red nozzle 55R via the temperature control medium discharge pipe 84.The temperature control medium 79 may be a cooling or heating medium,and is maintained at a temperature lower than the boiling point of thered EL solution 71R.

The green EL solution 71G stored in an organic material solution tank56G is kept at a proper temperature by a green EL solutionheat-insulating unit 86G. While the green EL solution 71G is kept atthis temperature, it reaches the green nozzle 55G via a green ELsolution supply pipe 57G. The heat-insulating unit 86G is set at a hightemperature in advance in consideration of a temperature by which thetemperature of the green EL solution 71G decreases by heat transfer tothe green EL solution supply pipe 57G or the like. When the green ELsolution 71G in the green nozzle 55G overheats or does not reach apredetermined temperature, the temperature control medium circulator 171supplies the temperature control medium 79 set to the predeterminedtemperature into the green nozzle 55G via a temperature control mediumsupply pipe 83G so as to set the green EL solution 71G to thepredetermined temperature. The temperature control medium circulator 171then receives the temperature control medium 79 in the green nozzle 55Gvia the temperature control medium discharge pipe 84. The temperaturecontrol medium 79 may be a cooling or heating medium, and is maintainedat a temperature lower than the boiling point of the green EL solution71G.

The blue EL solution 71B stored in an organic material solution tank 56Gis kept at a proper temperature by a blue EL solution heat-insulatingunit 86B. While the blue EL solution 71B is kept at this temperature, itreaches the blue nozzle 55B via a blue EL solution supply pipe 57B. Theheat-insulating unit 86B is set at a high temperature in advance inconsideration of a temperature by which the temperature of the blue ELsolution 71B decreases by heat transfer to the blue EL solution supplypipe 57B or the like. When the blue EL solution 71B in the blue nozzle55B overheats or does not reach a predetermined temperature, thetemperature control medium circulator 171 supplies the temperaturecontrol medium 79 set to the predetermined temperature into the bluenozzle 55B via a temperature control medium supply pipe 83B so as to setthe blue EL solution 71B to the predetermined temperature. Thetemperature control medium circulator 171 then receives the temperaturecontrol medium 79 in the blue nozzle 55B via the temperature controlmedium discharge pipe 84. The temperature control medium 79 may be acooling or heating medium, and is maintained at a temperature lower thanthe boiling point of the blue EL solution 71B.

The EL solutions 71R, 71G, and 71B are so set as to be independentlysprayed from the red nozzle 55R, green nozzle 55G, and blue nozzle 55B.The respective EL solutions 71R, 71G, and 71B may be kept at differenttemperatures in the red nozzle 55R, green nozzle 55G, and blue nozzle55B in accordance with the characteristics of solutes and solvents inthe EL solutions 71R, 71G, and 71B.

The red EL solution heat-insulating unit 86R, green EL solutionheat-insulating unit 86G, and blue EL solution heat-insulating unit 86Bmay keep the EL solutions 71R, 71G, and 7B at different temperatures.The temperature control medium circulator 171 may circulate differenttemperature control media 79 supplied from the temperature controlmedium supply pipes 83R, 83G, and 83B so as to set the EL solutions 71R,71G, and 71B to different temperatures.

The red nozzle 55R, green nozzle 55G, and blue nozzle 55B maysimultaneously spray the red EL solution 71R, green EL solution 71G, andblue EL solution 71B. Alternatively, after EL solution spray operationof a nozzle for a given color ends, a nozzle for another emission colormay start spraying another EL solution.

The amounts of the EL solutions 71R, 71G, and 71B sprayed to thecorresponding pixels may be different in accordance with characteristicssuch as the emission characteristics of emission materials in the ELsolutions 71R, 71G, and 71B, the solute solubility, and the solventvolatility. The kinds of solvents of the EL solutions 71R, 71G, and 71Bmay be appropriately different from each other.

The spray means of the nozzle 55 is piezoelectric in the aboveembodiments, but the present invention is not limited to this. Forexample, an electrostatic suction spray means may be employed. Theelectrostatic suction spray means charges the nozzle 55 and organic ELsolution 71. A small pressure is applied to the organic EL solution 71in the nozzle 55 to form the meniscus of the organic EL solution 71 inthe nozzle 55. In this state, a potential opposite in sign to that ofthe nozzle 55 is applied to the work table 51. An electrostaticattraction is applied to the organic EL solution 71 in the meniscusstate to suck the organic EL solution 71 from the nozzle 55.Accordingly, droplets of the organic EL solution 71 are sprayed from thespray port 55 a.

Alternatively, a thermal jet spray means may also be employed. Thethermal jet spray means instantaneously film-boils the organic ELsolution 71 in the nozzle 55 by a heating member. Bubbles are generatedin the organic EL solution 71 to change the internal pressure of thenozzle 55. As a result, droplets of the organic EL solution 71 aresprayed from the spray port 55 a. In the above some embodiments, thenozzle 55 is cooled to suppress generation of a gas of a solvent stayedin the nozzle 55. However, the solution spray apparatus is soconstituted as to permit an instantaneous solvent gas by heating of theheating member in the thermal jet spray means. That is, in the use ofthe thermal jet spray means, the nozzle 55 is so cooled as not togenerate any solvent gas except the purpose of spraying droplets.

Each of the above embodiments may adopt any one of the heat-insulatingunit 58, nozzle heat-insulating unit 59, substrate heat-insulating unit63, radial heater 64, heating unit 65, fan 66, heat insulator 67,temperature controller 76, temperature measurement unit 78, coolingmedium circulator 170, and temperature control medium circulator 171.The present invention is not limited to this, and a plurality of meansamong the heat-insulating means and measurement means may be arbitrarycombined to spray the EL solution.

According to the present invention, a droplet sprayed from the sprayport can easily evaporate, no landed droplet runs off from a surroundedregion, and no solutions in adjacent surrounded regions mix. Alarger-volume droplet of even a solvent a solubility in which is low canbe sprayed at once. Thus, the film formation time taken to form thesolute to a proper film thickness in the surrounded region can beshortened.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A solution spray apparatus comprising: at least one nozzle whichsprays at least one a droplet of a respective solution; a heater whichheats the solution in the at least one nozzle to a temperature lowerthan a boiling point of the solution; a temperature detector whichmeasures a temperature of the solution in the at least one nozzle; and atemperature controller which controls the heater so as to keep thetemperature of the solution in the at least one nozzle constant based onthe temperature measured by the temperature detector.
 2. The apparatusaccording to claim 1, wherein the at least one nozzle sprays an ELsolution.
 3. The apparatus according to claim 1, wherein said at leastone nozzle which sprays said respective solution comprises: a firstnozzle which sprays a first solution containing an EL material foxemitting light in a first color, and a second nozzle which sprays asecond solution containing an EL material for emitting light in a secondcolor different from the first color.
 4. The apparatus according toclaim 3, wherein the heater is controlled to set the first solution andthe second solution to different temperatures.
 5. A solution sprayapparatus comprising: at least one nozzle which sprays at least onedroplet of a respective solution; at least one tank which stores therespective solution and supplies the solution to the at least onenozzle; a unit which heats and insulates the solution in the at leastone tank; a temperature detector which measures a temperature of thesolution in the at least one tank; and a temperature controller whichcontrols the heating-insulating unit so as to keep the temperature ofthe solution in the at least one tank constant based on the temperaturemeasured by the temperature detector.
 6. The apparatus according toclaim 5, wherein the heating-insulating unit is controlled to set thetemperature of the solution in the at least one tank to be lower than aboiling point of the solution.
 7. The apparatus according to claim 5,wherein said at least one nozzle which sprays said respective solutioncomprises: a first nozzle which sprays a first solution containing an ELmaterial for emitting light in a first color, and a second nozzle whichsprays a second solution containing an EL material for emitting light ina second color different from the first color.
 8. The apparatusaccording to claim 7, wherein the at least one tank which stores therespective solution comprises a first tank which stores the firstsolution and a second tank which stores the second solution; and whereinthe heating-insulating unit is controlled to heat and insulate the firsttank and the second tank so as to set the first solution in the firsttank and the second solution in the second tank to differenttemperatures.